AB1395 UROLITHIN A AND B ACCELERATE MYOCYTE FUSION INTO MYOTUBES
Authors: Y. Henrotin, C. Lambert, A. Florin, J. Zappia, P. Centonze, C. Sanchez
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Urolithins are intestinal bacterial metabolites of ellagic acid, from pomegranate and nuts. They modulate oxidative-regulated pathways and display anti-inflammatory, antioxidative properties. Several studies indicate that they could be inducers of muscle strengthening. <h3>Objectives</h3> The aim of this in vitro study was to investigate their mechanisms of action at plasma concentrations on primary human myotubes. <h3>Methods</h3> Urolithin A and B (UA and UB) were evaluated separately on primary human muscle CD56+ cells, isolated from the vastus lateralis of 6 men and 3 women (aged range 55 to 96-y) and differentiated in myotubes. 24h-treatment mRNA-sequencing of these 9 patients was studied by DESeq2 analysis (R software). Modulation of several target genes was then validated in several concentrations (1-5 or 10 µM) by RT-qPCR and ELISA on 4 different patients. Organelles and cell morphology changes were observed by NanoLive CX-A live cell imaging during 72h. <h3>Results</h3> After 24h of treatment at 5 µM, UA and UB significantly modified the expression of 1779 and 319 genes, respectively (adjusted p-value of 0.01 and Log2FoldChange |&gt;0.32|). Among the most regulated genes, we found genes involved in myoblasts to myotubes differentiation. UA increased the expression of MYMX (+70%), PANX1 (+50%), MSTN (+64%), MYH2 (+28%) and conversely decreased FGF9 (-75%), MRLN (-33%), ICAM5 (-52%) and TGFBI (-55%). Regarding UB, it decreased IGFN1 (-75%), TGFBI (-60%) and increased MYH2 (+34%) and TGM2 (+59%). However, UA, but not UB, decreased DMD gene expression (-86%), a key factor in muscle strength, and MEF2C (-45%), a regulator of skeletal myogenesis. We also have observed the modulation of genes involved in the inflammatory process. They both induced a important decrease of CYP1B1 expression (-95%). Further, LIF was increased by 80% by UA and PTGS1 was decreased by 41% by UA and 43% by UB. UA and UB had the opposite effect on IL17B, a cytokine involved in tissue repair but its role in muscle is still to be defined. IL17B was decreased by 49% by UA and conversely upregulated by 45% by UB. In a second step, we confirmed the modulation of MYMX, PANX1, FGF9, ICAM5, PTGS1-PGE2, IL17B and TGFBI following UA and/or UB treatment at 1, 5 and 10 µM by RT-qPCR and ELISA. Finally, we also observed with live cell imaging that UA and UB increased myocyte fusion in myotubes, already after 6h of treatment. <h3>Conclusion</h3> UA and UB promote the differentiation process of myoblasts to myotubes. In parallel, urolithins present anti-inflammatory properties, mainly by reducing CYP1B1 expression and the PGE2 synthesis via PTGS1, but also for UA by increasing LIF. Our data provide a better understanding of urolithin activities and highlight their potential in the treatment of muscle disorders such as sarcopenia. <h3>References</h3> NA. <h3>Acknowledgement</h3> We would like to thank the staff of the GIGA ULiège Genomic Next Generation Sequencing platform for performing the RNA sequencing and of CIRM IN VITRO-SANTE platform for the live cell imaging. <h3>Disclosure of Interests</h3> Yves Henrotin Consultant of: Artialis SA Nestlé Expanscience Tilman Allegro Immubio, Cécile Lambert: None declared, Antoine Florin: None declared, Jérémie Zappia: None declared, Prescilia Centonze: None declared, christelle sanchez: None declared.